Everything You Need to Know About Grow Lights

Whether you’re just getting started in the plant world or have been an avid gardener for years, there’s one thing that’s stumped all of us at one time or another, and that’s grow lights.

In the past, grow lights were typically only used in professional greenhouses, but with the emergence of LEDs, you can now find a variety of grow lights alongside traditional light bulbs for home use. Unless you’re a light expert, there’s often some confusion when it comes to understanding the differences in lights and knowing which one to choose. Should you pay attention to watts or lumens? What about red and far-red spectrum light? We’re here to shine a light (pun intended) on grow lights, so you can utilize them for your plants at home.

Light and Plants

To best understand grow lights, let’s first look at the relationship between light and plants. Light plays a very special role in a plant’s life, and without it, wouldn’t be able to survive. As you might already know, light is absorbed through a process called photosynthesis. This process produces energy that’s then used to grow leaves, flowers, and branches. Just as gas makes a car go, light is the fuel to make your plant grow!

Light shines on the leaves and stems of the plant and gets converted to energy all day long or as long as there’s light available. As the light fades, you might think that the plant stops working, but in reality, the plant just switches gears. In the darkness, the plant converts that light energy into usable sugars to carry out important internal functions that we enjoy as a new leaf or flower. This cycle of harvesting energy during the day and expending the energy at night gets repeated over and over.

Lastly, the amount of time that light is shining on the plant and the amount of darkness it experiences is also part of the light-plant relationship. The length of the day influences how much energy can be harvested. In the spring and summer, we experience longer days, and therefore, more energy is to be made in a plant’s eyes. This is why you see fruit, flowers, and growth in the warmer months. In the winter, days are shorter, so some plants take the opportunity to store their energy until spring. This concept of light and darkness is used in the flower industry and the reason you can have daisies in the middle of winter. By altering the length of the day, you can trick a plant into thinking it's time to bloom!

Grow Lights vs. Natural Light

Grow light or natural light–which is best? The better question to ask is which one works for your situation. It’s a myth that grow lights are not as efficient as natural sunlight. Grow lights can actually be more efficient if used correctly. The best part is that light is light and your plant won’t care about the source of light, only that it’s present. So, don’t stress too much about it–just choose what works for you and your plant!

Natural light from the sun will always be the more convenient option. You don’t have to be responsible for turning it on and off, and the length of the day is automatically adjusted according to the season. The downside is that you can’t control the placement or intensity of the sun. A long period of overcast days might lower the sun's intensity that some of your plants require. And if your house faces north, for example, you can’t alter the sun to shine longer in a specific area.

The sun might be convenient, but it's not flexible or adjustable, which is where grow lights come in. Grow lights are available in many different forms. You’ll just need to remember to turn them on and off at the appropriate times during the year. Most grow lights can be combined with automatic timers that need to be programmed, but will do the work for you once set up! They’re consistent and reliable, making them predictable for plants, and in turn, causing them less stress. And they’re fully customizable for your needs, as long as you have the energy to power them.

Good-to-Know Grow Light Terms

There’s a lot of grow light terms that get thrown around that might be confusing to those of us that aren’t light experts. To make it easier, we’ve defined a few of the most common terms you’ll see on grow light packaging. Check them out below.

Intensity

Intensity is how bright the light is. For example, a light in a fridge will be less intense than headlights on a car. This is measured in two ways–in lumens (L) or on a Kelvin (K) scale. The brighter the light is, the more energy is available for the plant to use and the further one grow light bulb will reach in a given area. Lumens are a measure of the brightness as it appears to your eyes and Kelvin is the tone or temperature of the light, from warm (2700K) to cool (4100).

Watts

You might see the term “watts” associated with lumens or intensity, but wattage measures energy, not brightness. If a bulb requires a higher wattage number, it requires more energy, and thus, you can expect it to be brighter or more intense, providing a more productive light source for the plant.

Color

Not all grow lights have to be red or look white–some will appear yellow, blue or red. The color will vary according to the kind of light that the bulb is emitting. Keep the color in mind if you’re using the grow lights in your home since certain lights may irritate your eyes over time.

Duration

Duration is the length of time the light is on or off. Some grow lights will have a timer included, while other grow lights are just the bulb and nothing else. As explained above, the amount of time the light is on can influence the blooming and fruiting schedule of a plant.

Spectrum

Spectrum refers to the type of light that shines onto the plant and is measured in wavelengths (nm). The light spectrum we get from the sun ranges from the visible rainbow (ROYGBIV) to the invisible spectrum like UV and infrared light waves. Plants prefer to stay around the 400-700 nm range of light, as this is when they are the most productive.

Red and Far-Red Light Spectrum

Red and Far-Red light are part of the spectrum of colors that are 660 nm and 730nm respectively. Think of the two red lights as a switch where you can change how that energy is used within a plant by limiting the part of the spectrum you provide. This red spectrum is very helpful for fruiting or flowering plants and will be advertised as such on grow light packaging. So, if you see this, don’t think of the color red; think of the ‘limited spectrum for flowering and fruiting plants. This is for the really enthusiastic gardeners who want to “trick” their plants into flowering off of their normal schedule.

Full Spectrum

Full spectrum is the ideal choice if you have a mix of plants you’re growing or if the plants don’t flower or fruit often like a Fiddle Leaf Fig. Opposite the red and far-red light spectrum, full spectrum light has a larger portion of the spectrum of colors, making it a good all-around choice when choosing your bulb. Full spectrum does NOT mean you get all of the kinds of light available (no UV!), just the full spectrum that is right for the plant.

PAR

PAR is short for Photosynthetically Active Radiation. In simple terms, this is just the available light that is used to make energy for the plant. You most likely won't see this displayed on grow light packaging, but you will see PAR meters here and there when searching for grow lights. The PAR meter is just a tool that can measure how much of the light that is hitting the plant is actually usable (recall that plants like the range between 400-700nm).

Grow Light Options

As said before, you have options! Look around and find the right fit for your needs. To help, here’s a chart that compares some of the more popular kinds (and beginner friendly options) you’ll find out there.

**Infrared lights should be used with caution, as they’re designed to emit heat, not the wavelengths that plants need.

Choosing the Right Grow Light for You

1. First, see if a grow light is needed in your space. Light can be altered by a curtain or shade cloth if it’s too intense and container plants can always be moved. Try these methods before investing in an extensive grow light setup. When shopping for plants, it’s much easier to shop for the environment you already have rather than create a new one.
2. Find how strong or big of a light you need. Just like anything else, too much of a good thing can be a bad thing. One little house plant isn't going to need the same light power that five plants would, for example.

Bright Idea: 6-10 watts is plenty for one to a few house plants. If you need more, add another bulb or increase the wattage output. On average, 20 watts will cover 1 sq. ft. of area. So, 400 watts will cover about 9-12 sq. feet.

1. Go shopping! Choose a light that’s right for your plants. If you have multiple kinds of plants, go for a full spectrum light. If you’re after fruits and flowers, choose one more in the red spectrum. All of this should be printed on the grow light packaging, as well as the kinds of plants it’s best suited for.
2. Choose the right kind of bulb. Are you repurposing an old lamp? Then stick to a grow light that can screw into the standard light socket. Need a new lamp anyway? Look at grow lights that come already installed in a lamp.
3. Get picky! If the grow light is in your home, choose a set up that’s more stylish and blends in with your decor. If you have one in your greenhouse, then choose a less flashy setup. There’s also options for large and small areas, as well as ones with timers. Again, choose what works best for you.
4. It’s not an exact science. You might feel like you have to check all the boxes when choosing a bulb, but in reality, just stick to what feels right. After all, you can always move the light further away or turn it off sooner if needed.

Example: I have a Swiss Cheese Plant (shown below) that’s really struggling and needs more light where it’s placed on my shelf, but I’m in an apartment that faces the shady side of the building. I need something that doesn’t stand out or bug my eyes while still providing light. My solution was purchasing a low profile, full spectrum LED light that plugs into my wall. I chose one that also has a built-in timer and intensity settings for convenience.

How to Use Grow Lights

1. Set it up! Screw in the bulb and plug it in. Position the plant so that it’s no closer than 6 inches from the plant’s leaves.

• For multiple plants, arrange them so the plant needing the most light is closest to the light source and the one needing the least is furthest away.
• If an equal amount of light is required, evenly arrange the plants so that they’re equal distance to the light.

2. Turn it on in the morning as the sun comes up and try to stay consistent if you can. Plants like predictability.

3. Turn it off at the right time, depending on how much light your plant needs.

• Full sun: 13-16 hours per day
• Partial sun: 12-13 hours per day
• Shade or in combination with natural sunlight: 8-10 hours per day

Remember, a grow light is simply a lightbulb, just like any other light you use on a daily basis. The only difference is that we can choose the type and amount of light they emit. You don’t need to spend a lot of money on grow light equipment for them to be successful. Just read the labels armed with your new knowledge and choose with confidence! If you still need help, just call or message one of our plant specialists, and they’ll be happy to help!